This invention relates to valves for controlling the flow of fluids, and particularly to block-and-bleed valves assembled together to form manifolds for controlling the flow of fluids, especially liquid foods or beverages, from multiple sources to multiple delivery destinations. The invention represents a further modification and improvement of the manifold systems disclosed in my U.S. patent application Ser. No. 5,232,023 issued Aug. 3, 1993.
It is common in the food packaging industry to have a need to connect a number of sources of a fluid, such as different types of milk or different types of soft drinks, to a number of different filler machines to fill containers, such as gallons, half-gallons, quarts and so on. To date these connections have been accomplished in the form of a manifold, including a number of lines from the source tanks crossing a number of lines leading to the filler machines, with valves being provided to control flow of fluid from any selected one or more of the source tanks to any chosen one or more of the filler machines.
In the past, it has been conventional to use specially designed valves to control these manifolds, called block-and-bleed valves, sometimes called leak detector valves, with one such valve installed at each manifold intersection. Block-and-bleed valves are particularly applicable to the sanitary industry, because they permit control of flow of different types of fluids through the same valve with double protection against intermixing of those fluids. That is, it may be desirable to have chocolate milk flowing through one part of the valve and white milk through another part, or pasteurized milk through one part and raw milk through another part, or clean-in-place solution through one part and milk or another food fluid through another part. Clearly, it is critical that these fluids not be permitted to mix, and regulations require that even failure of a single seat or valve plug not permit such mixing.
While valves used in the past functioned generally satisfactorily, they were extremely complex and expensive, and included multiple, coaxial, independently operable actuators and valve plugs. Under certain circumstances these valves were subject to substantial leakage and product waste, and when they did fail in this manner, while preventing mix of different fluids, their maintenance was difficult and expensive.
Even the improved systems heretofore devised have suffered from the problem that, once the input and output valves in a particular valve assembly are closed and the drain or "leak detector" port opened, about one quart of the fluid, for example, milk, would be discharged out of the drain and, thus, wasted. A need has, thus, continued to exist for improved valve assemblies that are economical, readily controlled and which minimize waste of the fluids being conveyed.
In my above-noted patent there was shown a manifold valve assembly, that enables the use of three individually controllable valves to control the flow of fluids at each intersection in a manifold and in which each intersection is configured so that substantially all of the fluid can be drained by gravity flow prior to opening of the drain or leak detector port. In that assembly two of valves are combined in a single valve housing and use independently controllable coaxial actuators while a third valve is connected thereto by a short connecting conduit configured so that liquid will drain by gravity from the first two valves through the third to the delivery conduits. Independent control of a drain port that serves as a leak detector was provided for. Concentrically configured or coaxial actuator rods were used to enable independent control by means of simple actuators that are linearly aligned with each other. Both actuators and valve assemblies are readily removable as a single assembly for repair or replacement.
These valves, however, required the use of a cage attached to a bonnet which carried a valve seat against which one of the valve bodies worked. The need for such a cage has been found to significantly increase the cost of the manifold valve assemblies. A need has, thus, continued to exist for improved, economical valve systems.